According to a new paper published in Genome Biology and Evolution by Oxford University Press, the ringed sea snake, a species of venomous snake found in the oceanic waters around Australia and Asia, appears to have evolved to see an expanded palette of colors after losing its ancestors. this ability to respond to a changing environment.
Animal color vision is primarily determined by genes known as visual opsins. While opsin genes have been lost many times during the evolution of tetrapods (a group that includes amphibians, reptiles, and mammals), the emergence of new opsin genes is extremely rare. Before this study, the only known evolution of new opsin genes in reptiles appeared to have occurred in Helicops, a South American snake genus.
This study investigated the visual opsin genes in five ecologically distinct species of elapid snakes using published reference genomes. The history of the elapids, a family of snakes that includes cobras and mambas and the annulate sea snake, provides an opportunity to study the molecular evolution of vision genes.
During the low-light burrowing phase, early snakes lost two visual opsin genes and could perceive only a limited range of colors. However, some of their descendants now live in brighter environments; two elapid lineages have even moved from terrestrial to marine environments in the past 25 million years.
The aborted sea snake has four intact copies of the opsin gene SWS1, according to the researchers. Two of these genes are ancestrally sensitive to ultraviolet radiation, and two have evolved a new sensitivity to the longer wavelengths that dominate oceanic habitats.
The study authors believe that this sensitivity may give the snakes better color discrimination to distinguish predators, prey or potential mates from the colorful marine background. This differs dramatically from the evolution of opsins in mammals such as bats, dolphins, and whales during ecological transitions; noted further loss of opsin as they adapted to low light and aquatic environments.
“The earliest snakes lost much of their ability to see colors because of their burrowing lifestyle in dim light,” said the paper’s lead author Isaac Rossetto. “However, their sea serpent descendants now inhabit brighter and more spectrally complex marine environments. We believe that recent gene duplications have dramatically expanded the range of colors that sea snakes can see. By comparison, we humans have a similarly widespread color sensitivity, while cats and dogs are partially colorblind, much like these early snakes.”
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